A/C inop in max setting

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2002 Chevy 1500 Express Conversion van. A/C works fine except when you select the highest setting on the blower switch, quits blowing. Does this in either A/C or Max A/C setting.

Anyone have any ideas of what to replace/check?
 
Sometimes the highest speed is on a different electrical circuit than the lower speeds. Diagnosing that circuit is key, and you probably should have a service manual. In any case, check all fuses and relays related to the air conditioner and you might be able to solve the problem.

This is also why in some situations, lower fan speeds don't work, but maximum speed does work.
 
Aren't these blowers often controlled by a set of resistors? Id suspect that the max speed is no resistor, or a minimal one. Regardless, I'd start there.

If it's PWM, then I think all the circuit hardware is used all the time, so then it would have to be a control issue Id think.
 
See if there is a blower fan relay. If so its probably bad. The relays have a low and a single full/high speed setting. They are known to go bad on a single side so it either works at full only or the lower settings only.
 
Wow, that's weird. Usually the resistor goes bad killing the slower speeds - my guess is the switch. Does it do it in modes other than A/C?
 
Check the BLOWER fuse in the underhood fuse block.
Unplug the Blower Resistor assembly harness & Check for melted plastic/overheated Terminals.
Blower on high/Key on...Check for 12 VDC on the Orange & Red wires at the blower resistor assembly connector.

*If you find melted Terminals....Replace the Resistor assembly & Connector along with the Blower Motor as it's probably drawing more continuous current than the connection at the resistor can support. Check Ground# G103 for cleanliness/tightness.

*If everything checks out good.....Replace the Resistor assembly, The High Blower Relay is built into the assembly.
 
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Originally Posted By: Jimzz
See if there is a blower fan relay. If so its probably bad. The relays have a low and a single full/high speed setting. They are known to go bad on a single side so it either works at full only or the lower settings only.



This. A GM thing.
 
Originally Posted By: clinebarger
Check the BLOWER fuse in the underhood fuse block.
Unplug the Blower Resistor assembly harness & Check for melted plastic/overheated Terminals.
Blower on high/Key on...Check for 12 VDC on the Orange & Red wires at the blower resistor assembly connector.

*If you find melted Terminals....Replace the Resistor assembly & Connector along with the Blower Motor as it's probably drawing more continuous current than the connection at the resistor can support. Check Ground# G103 for cleanliness/tightness.

*If everything checks out good.....Replace the Resistor assembly, The High Blower Relay is built into the assembly.



Thanks for the exact instructions!

Would you happen to know a link to a manual?
 
Originally Posted By: JHZR2
Aren't these blowers often controlled by a set of resistors?


Yep...Sounds like a bad Blower Motor Resistor.
 
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Originally Posted By: sasilverbullet

Thanks for the exact instructions!

Would you happen to know a link to a manual?


I used to subcontract to a subcontractor that worked on nothing but EMT vehicles when your van was new, I know the circuits by heart. The FSM's for your van can still be found in print.
 
Under the hood on the Passenger side on top of the heater housing to the left of the blower motor is where the resister screws in(its rectangular). pull the plug to it and to the motor, check for melt. Most likely need a new resistor.
 
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Originally Posted By: sasilverbullet
2002 Chevy 1500 Express Conversion van. A/C works fine except when you select the highest setting on the blower switch, quits blowing. Does this in either A/C or Max A/C setting.

Anyone have any ideas of what to replace/check?

Just AC, or when calling for heat as well?
 
Have you checked with specific chevy forum?
If there is a common issue, they usually have better experience on the solutions from members.

Nothing against this forum but it is a variety of different brand of vehicle owners which is not necessarily just Chevy or GM.
 
Last edited:
Originally Posted By: sasilverbullet
2002 Chevy 1500 Express Conversion van. A/C works fine except when you select the highest setting on the blower switch, quits blowing. Does this in either A/C or Max A/C setting.

Anyone have any ideas of what to replace/check?


So , high fan speed does not work ? Does it do or not do the same thing on heat or defrost .

The older cars had a resister network that gave you the older speeds & high was direct 12 VDC to the fan .

Follow the advice to locate a wiring diagram / schematic .

Wyr
God bless
 
Thanks for the pointers!
cheers3.gif


Yep, plug and connector fried, so I ordered them both on RockAuto along with a AC Delco Blower motor. Not taking any chances on a 16 yr old van.

Pics...

 
When you get the new connector......Unpin the 4 good wires & transfer them to the new connector, This way you will only have to splice the two high amp wires.
It really bugs me when people splice wires for no reason!
 
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